Imaging system

ABSTRACT

An electrophoretic imaging system is described in which a particulate image is transferred to a receiving sheet having a water tackifiable surface. The surface is moistened, pressed against the image and dried. In a preferred embodiment, the water tackifiable material is converted to a water insoluble form by heat after transfer of the image.

United States Patent ,1191

Carreira July 29, 1975 IMAGING SYSTEM [56] References Cited [75] Inventor: Leonard M. Carreira, Penfield, UNITED STATES PATENTS N.Y. 3,383,993 5/1968 Shu-l-lsiung Yeh 355/3 P 3,384,565 5/1968 Tulagin et a1 [73] Asslgneei Cowman, Stamford 3,791,823 2/1974 Carreira 96/l.4

Conn.

[22] Filed: Aug. 20, 1973 Primary ExaminerSamuel S. Matthews Assistant Examiner-Kenneth C. Hutchison [2]] Appl' 389917 Attorney, Agent, or FirmJames J. Ralabate; David C.

Related U.S. Application Data Petre; Charles E. Smith [60] Division of Ser. No. 12,366, Feb. 18, 1970, Pat. No.

3,791,823, which is a continuation of Ser. No. 57 ABSTRACT 808,921, March 20, 1969, abandoned, which is a continuation of Ser. Nos. 677,706, Oct. 24, 1967, P System descr'bed m abandoned Ser. 677,707, Oct 1 24, 1967, which a particulate 1mage 1s transferred to a receiving abandoned, and s 459,360, May 23 9 5 sheet having a water tackifiable surface. The surface is b ndoned, moistened, pressed against the image and dried. In a preferred embodiment, the water tackifiable material [52] U.S. Cl 355/3 P; 204/300 PE is converted to a water insoluble form by heat after [51] Int. Cl G03g 15/22 transfer of the image. [58] Field 0fSearch...355/3 P; 204/181 PE,299 PE.

204/300 PE; 96/1 PE, 1.4, 1.2, 1.3

2 Claims, 2 Drawing Figures SHEET PATENTEI] JUL 2 9 I975 IMAGING SYSTEM CROSS-REFERENCE TO RELATED APPLICATION This is a division of application Ser. No. 12,366, filed Feb. 18, 1970, now U.S. Pat. No. 3,791,823, issued Feb. 12, 1974, which was a continuation of now abandoned application Ser. No. 808,921, filed Mar. 20, 1969, which in turn was a continuation of now abandoned applications Ser. Nos. 677,706 and 677,707, both filed Oct. 24, 1967, and 459,860, filed May 28, 1965.

BACKGROUND OF THE INVENTION This invention relates in general to imaging systems and more specifically, to an improved electrophoretic imaging system.

There has been recently developed an electrophoretic imaging system capable of producing color images which utilizes electrically photosensitive particles. This process is described in detail and claimed in U.S. Pat. Nos. 3,384,565 and 3,384,566 issued May 21, 1968 to H. E. Clark and V. Tulagin et al respectively. In such an imaging system, variously colored light-absorbing particles are suspended in a non-conductive liquid carrier. The suspension is placed between electrodes, subjected to a potential difference and exposed to an image. As these steps are completed, selective particle migration takes place in image configuration, providing a visible image at one or both of the electrodes. An essential component of the system is the suspended particles which must be electrically photosensitive and which apparently undergo a net change in charge polarity upon exposure to activating electromagnetic radiation, through interaction with one of the electrodes. In a monochromatic system, particles of a single color may be used, producing a single colored image equivalent to conventional black-and-white photography. In a polychromatic system, the images are produced in natural color because mixtures of particles of two or more different colors which are each sensitive only to light of a specific wavelength or narrow range of wavelengths are used. Particles used in this system must have both intense and pure colors and be highly photosensitive.

After the exposure and particle migration steps are completed, the electrodes are separated and the carrier liquid is allowed to evaporate. This leaves images on one or both of the electrodes made up of selectively deposited particles. The carrier liquid may contain a small proportion of a wax or other binder which would serve to bind the particles together in the images. However, if more than a very small amount of binder material is used, undesirable interference with the imaging process takes place. Thus, the images are at this time in a fragile and easily damaged condition. It has been suggested that a transparent sheet be laminated over the images, or a transparent binder resin be sprayed over the images to form a protective coating. While, when carefully done, these techniques will protect the image, the image is often damaged during the application of the protective material. These protective techniques are not suitable for a mechanized system. Also, when it is desired to transfer the image from the electrode material to a receiving sheet, the dangers of smudging or otherwise damaging an unfixed image is very great. Thus, there is a continuing need for a better system for fixing the particulate image formed on the electrode surface and/or for permitting transfer of said image to a receiving sheet.

A method of transferring and fixing formed electrophoretic images from the imaging electrode using thermo-adhesive coated sheets has recently been developed. This process is disclosed and claimed in copending application Ser. No. 459,860, filed June 28, 1965. For this process, a transfer sheet is prepared by coating onto the surface of a sheet, such as paper, a layer comprising a thermosolvent dispersed in a binder. The thermosolvent has the characteristics of being a solid at ordinary temperatures but melting slightly above ordinary temperatures. When melted, this thermosolvent dissolves the binder resin making the coating surface very tacky. In electrophoretic imaging, after the image has been formed on the injecting electrode, the thermoadhesive coated sheet is heated above the melting temperature of the thermosolvent and the sheet is pressed against the particulate image. The sheet is then cooled leaving a fixed image embedded in the surface of the thermo-adhesive layer. This system is capable of transferring substantially all of the particles from the electrode surface and of giving good abrasion resistance after cooling. However, this system requires specially coated sheets and adds the need for the heating step before transfer.

Electrophoretic methods for transferring images formed on the injecting electrode to a receiving sheet are described and claimed in copending applications Ser. No. 542,050, filed Apr. 12, 1966, now U.S. Pat. No. 3,565,614, and Ser. No. 542,051, filed Apr. 12, 1966, now abandoned. Here, transfer is accomplished by placing the receiving sheet over the formed image, subjecting the formed image to a potential applied between the injecting electrode and the receiving sheet while actinic electromagnetic radiation is directed against the formed image. When the transfer sheet is stripped away, substantially all of the image particles go with it. The transfer sheet may have a pressure sensitive adhesive on the surface thereof to aid in complete transfer. This is a simple and effective transfer method. However, the image on the receiving sheet is not fixed and is subjected to smudging or other damage.

SUMMARY OF THE INVENTION It is, therefore, an object of this invention to provide a method of fixing a particulate electrophoretic image which overcomes the above-noted disadvantages.

It is another object of this invention to provide a method of transferring an electrophoretic image to a receiving sheet and fixing the image thereto.

It is still another object of this invention to provide a method of protecting an electrophoretic image from damage.

It is still another object of this invention to provide an electrophoretic imaging method capable of producing imaged sheets which may be handled without damage thereto.

It is still another object of this invention to provide an inexpensive and non-toxic system for transferring electrophoretic images to receiving sheets and fixing the images thereto.

The foregoing objects and others are accomplished in accordance with this invention by providing a transfer system utilizing a transfer sheet consisting of a paperlike material having incorporated therein an ingredient which is at least partially water softenable and/or tack- 3 4 ifiable. The sheet is used in a process in which a particalcohol, sodium alginate, copolymers of methylvinulate electrophoretic image is formed, the transfer ylether and maleic anhydride', cellulosics such as sheet is brought into contact with the particulate immethyl cellulose, ethyl cellulose, hydroxy ethyl celluage, and the particles are transferred to it, the transfer lose, cyano ethyl cellulose; starch derivatives such as sheet and image is then contacted with moisture to 5 oxidized starches, enzyme conversions, dextrine consoften and tackify the transfer sheet whereby the partiversions, amylose, amylpectin; casein; proteins such as cles are embedded in the sheet and the residual moisgelatin, nucleo protein, poly(surcosane), sericin; other ture is evaporated from the sheet leaving a fixed image. polysaccharides such as algenic acids, gum arabic, gum The image sheets produced by this process are surpristragacanth, heparin, pectin; and mixtures thereof. If deingly resistant to handling and abrasive contact. It is not sired, the water soluble material may also include a pigfully understood why the particles are so well fixed to ment, such as clay, titanium dioxide, calcium carbonthe paper-like sheet. However, it appears that the moisate; a dispersing agent, a'plasticizer, a wetting agent, ture tends to swell and slightly separate the paper fibers etc. so that the very small image particles are entrapped be- While images fixed with the water soluble material of tween the fibers. Also, the water soluble or tackifiable this invention give an excellent fix with good rub resisingredient tends to adhesively bind the particles to the tance, the degree of fix may be adversely affected by paper. later Contact with moisture. This moisture sensitivity may be overcome where the soluble material is con- These receiving sheets are exceptionally inexpensive rt d to an insoluble form by the moisture and heat since the added ingredient can be incorporated into the d i g fixi g, Any suitable thermosetting material may paper during the paper making process. In fact. as is be used. Typical materials include mixtures of polyvipointed t below. many of the Z g ag ts, u as nyl alcohol and copolymers of methyl vinyl ether and starch and gelatin, which are normally incorporated maleic anhydride; unsaturated water soluble polyesters into paper during the paper making process are at least such as the condensation product of fumaric acid, polypartially water soluble or tackifiablc so that many conethylene glycol, and pentaerythritol when mixed with ventional papers may be used in this process. Since no water soluble diacrylate; for example, tetramethylene coatings need to be applied to substrates, the transfer glycol, dimethacrylate, can be used as a water soluble sheets are more economical to produce than those used thermosetting medium. The following structure is reppreviously. Further, since only water is necessary to resentative of such a water soluble polyester;

soften sheets, no toxic volatile materials need to be water soluble thermosetting acrylic polymers which are used which may be hazardous to operators of machines prepared by acid/acrylate ester copolymerization using the process of this invention. The final image crosslinked with hexakis (methoxymethyl) melamine sheet appears to contain an image in the surface of orto convert them to a water insoluble state represented dinary paper. For many copying purposes this is desirby the following structure:

CH-CH c H -ca l C C O 0 O O- x R NH Y Polymer HO0C I l C C O ll N cn ocn, N cape-l: C-N H+ C-H --b CH OCH CHQOCHH +CHHOH C rosslinked Polymer able since the final product will have the appearance of Polyvinyl alcohol can be crosslinked with aldehydes,

a printed paper sheet. for example, crotonaldehyde. These thermosetting The water softenable or tackifiable ingredient may water soluble materials are considered to form a precomprise any suitable material. Typical water soluble ferred embodiment of this invention because of their materials include water soluble resins such as polyvinyl outstanding resistance to moisture damage after fixing.

BRIEF DESCRIPTION OF THE DRAWINGS The advantages of this improved electrophoretic imaging system will become apparent upon consideration of the following detailed disclosure of the invention, especially when taken in conjunction with the accompanying drawings, wherein:

FIG. 1 shows a side view of a simple exemplary system for carrying out the process of this invention wherein the blocking electrode and the transfer sheet are in roller configuration.

FIG. 2 shows a second embodiment of an exemplary system for carrying out this process wherein the transfer sheet is in the form of a tractor mounted web.

Referring now to FIG. 1, there is seen a transparent electrode generally designated 1 which, in this exemplary instance, is made up of a layer of optically transparent glass 2 overcoated with a thin optically transparent layer 3 of tin oxide, commercially available under the name NESA glass. This electrode will hereafter be referred to as the injecting electrode. On the surface of injecting electrode 1 is coated a thin layer 4 of finely divided photosensitive particles dispersed in an insulating carrier liquid. The term photosensitive, for the purposes of this application, refers to the properties of a particle which, once attracted to the injecting electrode, will migrate away from it under the influence of an applied electric field when it is exposed to actinic electromagnetic radiation. For a detailed theoretical explanation of the apparent mechansim of operation of the imaging process, see the abovementioned copending application Ser. Nos. 384,737, now U.S. Pat. No. 3,384,565 and 384,681, now U.S. Pat. No. 3,384,566, the disclosures of which are incorporated herein by reference. Adjacent to the liquid suspension 4 is a second electrode 5, hereinafter called the blocking electrode which is connected to one side of the potential source 6 through a switch 7, the opposite side of potential source 6 is connected to the injecting electrode 1 so that when switch 7 is closed, an electric field is applied across the liquid suspension 4 between electrodes 1 and 5. An image projector made up of light source 8, a transparency 9, and a lens 10 is provided to expose the dispersion 4 to a light image of the original transparency 9 to be reproduced. Electrode 5 is made in the form of a roller having a conductive central core 11 connected to the potential source 6. The core is covered with a layer of blocking electrode material 12, which may be insulating or substantially insulating, typically Baryta paper or Tedlar (a polyvinyl fluoride film available from E. I. du Pont de Nemours & Company). The pigment suspension is exposed to the image to be reproduced while a potential is applied across the blocking and injecting electrodes by closing switch 7. Roller 5 is caused to roll across the top surface of injecting electrode 1 with switch 7 closed during the period of image exposure. This light exposure causes exposed particles orginally attracted to injecting electrode l to migrate through the liquid and adhere to the surface of the blocking electrode, leaving behind a particulate image on the surface of injecting electrode 1 which is a duplicate of the original transparency 9. At this time, the particulate image on the injecting electrode is very fragile and subject to damage. Also since the injecting electrode is itself often rather expensive and fragile, it is desirable to transfer the formed image to a receiving sheet and fix the image thereon. In the embodiment shown in FIG. 1, there is provided a transfer roller generally designated 13 to which the formed image may be transferred and fixed. Transfer roller 13 consists of a hollow conductive core 14 surrounded by a layer of substantially insulating material 15. Layer 15 includes a material which is at least partially soluble or tackifiable in water. As is further discussed below, this material may be a conventional water-soluble sizing agent incorporated into a paper sheet during conventional paper-making operations. Such a paper sheet is a preferred material for us as layer 15. The surface of conductive core 14 in contact with the inner surface of layer 15 is preferably perforated or screen-like so that moisture, typically in the form of steam, may be admitted into hollow core 14 and contact layer 15 to heat and/or moisten layer 15. Means may also be provided to admit hot, dry air or to otherwise heat layer 15 to evaporate residual moisture therefrom after transfer of an image from injecting electrode 1 to layer 15. The conductive core of transfer roller 13 is connected through switch 16 and power supply 17 to the injecting electrode. It should be noted that the potential applied to the core of the transfer roller is opposite in sign to that applied to the core of the blocking electrode. After the image has been formed on the surface of injecting electrode 1, switch 16 is closed and transfer roller 13 is passed across the surface of injecting electrode 1. The layer 15 is then moistened thereby softening and tackifing layer 15. This permits the image particles to penetrate the surface of layer 15 and be embedded therein.

If desired, transfer roller 13 may be passed across the formed image without the application of a field across the image layer between transfer roller 13 and injecting electrode 1. Satisfactory transfer of the particulate image to the transfer roller surface will occur. However, it is preferred that a potential be applied to the core of the transfer roller opposite is sign to that applied to the core of the blocking electrode to aid com plete transfer of the particulate image. This results in more complete image transfer thus producing an image of higher density. Also, since fewer particles are left on the surface of injectingelectode l, the problems of cleaning this electrode before the formation of subsequent images is reduced.

While it is not necessary that the image layer be illuminated during the transfer operation, it often increases efficiency to either project the original image onto the injecting electrode surface or to flood this surface with white light. If desired, color balance of a polychromatic image may be corrected by flooding the injecting electrode with filtered white light during transfer. Such color correction is more fully described in copending application Ser. No. 542,050, filed Apr. 12, 1966.

FIG. 2 shows a second embodimentof a system for continuously forming a photoelectrophoretic image, transferring the image to a transfer sheet and fixing the image thereon. Here, the transparent injecting electrode 1 and the blocking electrode 5 are the same as in the above-discussed embodiment of FIG. 1. Also, the exemplary system for projecting an image onto the photosensitive suspension is the same as that of FIG. 1.

Here, however, a tractor 18 is coupled to the blocking electrode 5 to automatically transfer and fix the positive image formed on the NESA glass surface 3. The tractor 18 comprises a frame 19 which supports the blocking electrode and image transfer means for movement across the imaging surface. The transfer means consists of a continuous transfer web of substantially insulating material, e.g., paper which contains an ingredient which is at least partially soluble in water. The web is mounted on supply roller 21 and is adapted to pass in contact with guide rollers 22 and 23 on its way to take up roller 24. Guide Roller 22 is hollow and has a perforated or screen-like surface. A conduit 25 is provided to introduce moist air or steam into guide roller 2. Shield means is provided to prevent excess leakage of the moist air or steam. The moisture softens and tackifies web 20 to permit the particulate image to become embedded therein. Guide roller 23 is provided, if desired, with means to heat and thus dry web 20. The heating means may consist, for example, of steam admitted through conduit 26 to the interior of closed roller 23. In operation, a mixture of photosensitive particles in a substantially insulating carrier liquid is coated onto injecting electrode 1. The photosensitive mix is exposed to an image with switch 7 closed and the tractor and blocking electrode are moved from left to right across the imaging surface. As the blocking electrode passes the imaging surface, unwanted particles migrate to the blocking electrode surface leaving a positive particulate image conforming to transparency 9 on the NESA glass surface 3. As the tractor reaches the NESA surface, web 20 contacts the NESA surface 3 without relative movement with respect thereto. The particulate image becomes embedded in the softened transfer web 20. Then as the transfer web 20 leaves the injecting electrode surface, residual moisture evaporates and the web rehardens. Of course, the imaged transfer roller 20 would not necessarily be rolled upon itself on roller 24. Alternatively, the web could be fed to a cutting means which would cut each image area from web and feed the individual sheets to a receiving tray. When the tractor and blocking electrode reach the end of their travel, brush 27 cleans unwanted pigments from the surface of blocking electrode 5. The tractor is then raised slightly and returned to the starting position without again contacting the injecting electrode surface. Dashed line 28 schematically indicates the path taken by axle 29 of the blocking electrode during the imaging and return movements. As can be seen, the device schematically represented is capable of continuously forming, transferring, fixing and storing photoelectrophoretic images.

Any suitable photosensitive particle or mixtures of such particles may be used in carrying out the imaging process, regardless of whether the particular particle selected is organic, inorganic and is made up of one or more components in solid solution or dispersed one in the other or whether the particles are made up of multiple layers of different materials. Typical photosensitive particles include organic pigments such as those listed in copending application Ser. No. 655,022 filed July 21, 1967 now US. Pat. No. 3,384,488 issued May 21, 1968 to V. Tulagin and L. Carreira the disclosure of which is incorporated herein by reference.

As stated above, any suitable particle structure may be employed. Typical particles include those which are made up of only the pure photosensitive material or a sensitized form thereof, solid solutions or dispersions of the photosensitive material in a matrix such as thermoplastic or thermosetting resins, copolymers of photosensitive pigments and organic monomers, multilayers of particles in which the photosensitive material is included in one of the layers and where other layers provide light filtering action in an outer layer or a fusible or solvent softenable core of resin or a core of liquid such as dye or other marking material or a core of one photosensitive material coated with an overlayer of another photosensitive material to acheive broadened spectral response. Other photosensitive structures in clude solutions, dispersions, or copolymers of one photosensitive material in another with or without other photosensitively inert materials. Other particle structures which may be used but which are not required include those described in US. Pat. No. 2,940,847 to Kaprelian.

Although various electrode spacings may be employed, spacings of less than 1 mil and extending down even to the point where the electrodes are pressed together as in the case of the roller electrode constitute a particularly preferred form of the invention in that they produce better resolution and superior color separation results than is produced with wider spacings. This improvement is believed to take place because of the high field strength across the suspension during imaging.

In a monochromatic system, particles of a single color, for example, are dispersed in the carrier liquid and exposed to a black-and-white image. A single color image results, corresponding to black-and-white photography. In a polychromatic system, the particles are selected so that those of different colors respond to different wavelengths in the visible spectrum corresponding to their principal absorption bands. Also, the pigments should be selected so that their spectral response curves do not have substantial overlap, thus allowing for color separation and subtractive multi-color image formation. In a typical subtractive multi-color system, the particle dispersion should include cyan colored particles sensitive mainly to red light, magenta particles sensitive mainly to green light and yellow particles sensitive mainly to blue light. When mixed together in a carrier liquid, these particles produce a black appearing liquid. When one or more of the particles are caused to migrate from the injecting electrode towards the blocking electrode, they leave behind particles which produce a color equivalent to the color of the impinging light. Thus, for example, red light exposure causes the cyan colored particles to migrate, leaving behind the magenta and yellow particles which combine to produce red in the final image. In the same manner, blue and green colors are reproduced by the removal of yellow and magenta respectively. When white light impinges upon the mix, all particles migrate, leaving behind the color of the white or transparent substrate. No exposure leaves behind all pigments which combine to produce a black image. This is an ideal technique of subtractive color imaging in that the particles are not only each composed of a single component but, in addition, they perform the dual functions of final image colorant and photosensitive medium.

DESCRIPTION OF PREFERRED EMBODIMENTS The details and advantages of the fixing process of the present invention will be further understood upon reference to the following examples. All parts and percentages are by weight unless otherwise indicated. The following examples should be considered to constitute preferred embodiments of the fixing process of this invention. I g

In each of the examples below, a suspension including three different colored pigments is made up by dispersing the pigments in finely divided form in an insula'ting carrier liquid. This mixture may be referred to as tri-rnix. In each case, the imaging and transfer operations are carried out using an apparatus of the sort schematically shown in either FIG. 1 or FIG. 2, with the imaging mix coated on a NESA glass substrate through which exposure is made. The NESA glass surface is connected in series with a switch, a potential source, in the conductive center of a roller having a coating of Baryta paper on its surface. The roller is approximately 2 /2 inches in diameter and is moved across the plate surface at about 4 centimeters per second. The plate employed is roughly 3 inches square and is exposed to a light intensity of about 1,200 foot-candles as measured on the uncoated NESA glass surface. In each case after the blocking electrode has moved across the injecting electrode surface leaving a positive image on the injecting electrode surface the transfer roller or tractor is then passed across to receive the image particles. Where a roller configuration is used, the transfer roller is approximately 2 /2 inches in diameter and is moved across the plate surface at about 4 centimeters per second. Where the tractor configuration is used, each of the two web support rollers is approximately 3 inches in diameter and the tractor is moved across the plate surface at about 4 centimeters per second. Provision is included for imposing a potential between the transfer rollers and the injecting electrode having a sign opposite to that imposed on the blocking electrode core during imaging. Unless otherwise indicated, the blocking electrode roller is held at a negative potential of about 2,500 volts with respect to the substrate.

EXAMPLE I A sheet of ordinary bond paper is dipped into a solution of about 3 weight percent arrowroot starch (available from Will Scientific Co.) dissolved in water. The paper is dried using the radiant energy of a General Electric infrared industrial lamp. The dried paper is wrapped around the transfer roller in an electrophoretic imaging device of the sort shown schematically in FIG. 1. A polychromatic imaging tri-mix is prepared consisting of a cyan pigment, Monolite Fast Blue GS, the alpha form of metal-free phthalocyanine, available from E. I. du Pont de Nemours & Co.; a magenta pigment, Naphthol Red B, C. I. No. 12355, l(2-methoxy- 5-nitrophenylazo)-2-hydroxy-3-nitro-3- naphthanilide, available from Collway Colors; and a yellow pigment, 8,1 3-dioxodinaphtho-( 1 ,2-2,3)- furan-6-carbox-p-methoxyanilide, prepared by the method described in copending application Ser. No. 421,377, filed Dec. 28, 1964, now US. Pat. No. 3,448,029. About 8 parts of a mixture of finely divided pigments is dispersed in about 100 parts Sohio Odorless Solvent 3440, a kerosene fraction available from the Standard Oil of Ohio. The imaging suspension is coated onto the NESA glass surface and is exposed to a conventional Kodachrome transparency while the blocking electrode is passed across its surface. Immediately thereafter the transfer roller is passed across the NESA glass surface with a potential applied having a sign opposite to that used during imaging. This electrophoretic transfer step is further described in copending application Ser. No. 542,050, filed Apr. 12, 1966. A loosely adhering powder image is observed on the surface of the transfer sheet, conforming to the original. After allowing residual carrier liquid to evaporate, the image bearing transfer roller is brought into contact with a perforated metal roller having steam admitted to its interior. The steam contacts the transfer roller moistening and heating its surface while the particles are being pressed into firm contact therewith. The transfer sheet is then allowed to cool to room temperature and residual moisture is allowed to evaporate. An excellent image, conforming to the original, well fixed and resistant to rubbing contact is observed on the transfer sheet.

EXAMPLE II The image forming transfer and fixing steps of Example I are repeated except that in this instance the transfer sheet is ordinary newsprint and is dipped into a 7 weight percent solution ofCarbowax 4000, a polyethylene glycol available from the Union Carbide Chemical Co. This transfer sheet is dried, wrapped around the transfer roller and an image is formed and transferred thereto as in Example I. After application of heat and moisture as in Example I, an excellent image corresponding to the original with a good fix in and on the surface of the transfer sheet is observed.

EXAMPLE III An imaging suspension is prepared consisting'of a cyan pigment, Cyan Blue GTNF, C. I. No. 74160, the beta form of copper phthalocyanine, available from Collway Colors; a magenta pigment, Watchung Red B, C. I. No. 15865, l-(4-methyl-5-chloroazobenzene-2'- sulfonic acid)-2hydroxy-3-naphthoic acid, available from E. I. du Pont de Nemours & Co. and a yellow pigment, Algol Yellow GC, C. I. No. 67300, l,2,5,6- di(C,C-diphenyl)-thiazole-anthraquinone, available from General Dyestuffs. About 7 parts of this mixture of finely divided pigments is dispersed in about parts of Isopar-G, a long chain saturated aliphatic hydocarbon available from Humble Oil Company of New Jersey. A transfer sheet is prepared by dipping a sheet of ordinary bond paper into a solution of about 5 percent by weight Gantrez AN-l 39, a copolymer of methyl vinyl ether and maleic anhydride, available from General Aniline & Film Corp. and about 5 weight percent polyvinyl alcohol, 99 percent hydrolized, available from Matheson, Coleman & Bell, in water. The resulting transfer sheet is dried and wrapped on a spool in a device of the sort shown in FIG. 2. The imaging suspension is coated onto the NESA glass electrode and the blocking electrode is passed across its surface while a potential is imposed across the imaging suspension and the suspension is exposed to a polychromatic image using a conventional Kodachrome original. After allowing the residual Isopar-G to evaporate, the tractor is passed across the image on the injecting electrode. Steam is emitted into the first roller moistening and slightly heating the transfer paper. The second roller further heats the transfer sheet to a temperature of about C. to cause the thermosetting reaction in the resin mixture which now bonds the formed image. The image produced is of excellent quality, well fixed to the transfer sheet. The image is resistant to abrasion, even in the presence of moisture.

Although specific components and proportions have been described in the above examples, other materials as listed above, where suitable, may be used with similar results. In addition, other materials may be added to the imaging suspension or transfer material to synergize, enhance, or otherwise modify their properties. For example, the transfer material may have colorants, plasticizers, wetting agents, etc. added thereto, if desired.

Other modifications and ramifications of the present invention will occur to those skilled in the art upon a reading of the present disclosure. These are intended to be included within the scope of this invention.

What is claimed is:

1. Photoelectrophoretic imaging apparatus comprising:

a. a pair of closely spaced apart electrodes at least one of which is partially transparent, said electrodes adapted to have an imaging suspension comprising a mixture of electrically photosensitive particles in a substantially insulating liquid introduced therebetween;

b. means to project a light image on an imaging suspension between and in contact with said electrodes through said partially transparent electrode;

c. means to apply an electric field across an imaging suspension that may be between said electrodes;

d. means to separate said electrodes from said closely spaced relationship leaving an image corresponding to said projected image on one of said electrodes;

e. a transfer sheet comprising a water tackifiable material;

f. means to moisten said transfer sheet with water;

g. means to bring said transfer sheet into firm contact with said image on said one electrode; and

h. means to separate said transfer sheet from said one electrode and remove residual moisture therefrom so that saidparticles become fixed in and on the surface of said transfer sheet.

2. Apparatus according to claim 1 wherein said water tackifiable material is a thermal setting material and means are provided to heat said transfer sheet above the thermal setting temperature of said material after said particles are embedded in the surface of said sheet. l 

1. Photoelectrophoretic imaging apparatus comprising: a. a pair of closely spaced apart electrodes at least one of which is partially transparent, said electrodes adapted to have an imaging suspension comprising a mixture of electrically photosensitive particles in a substantially insulating liquid introduced therebetween; b. means to project a light image on an imaging suspension between and in contact with said electrodes through said partially transparent electrode; c. means to apply an electric field across an imaging suspension that may be between said electrodes; d. means to separate said electrodes from said closely spaced relationship leaving an image corresponding to said projected image on one of said electrodes; e. a transfer sheet comprising a water tackifiable material; f. means to moisten said transfeR sheet with water; g. means to bring said transfer sheet into firm contact with said image on said one electrode; and h. means to separate said transfer sheet from said one electrode and remove residual moisture therefrom so that said particles become fixed in and on the surface of said transfer sheet.
 2. Apparatus according to claim 1 wherein said water tackifiable material is a thermal setting material and means are provided to heat said transfer sheet above the thermal setting temperature of said material after said particles are embedded in the surface of said sheet. 